Hiding a device

ABSTRACT

The object of the invention is a method where a first communications device ( 10 ) and a second communications device ( 20 ), previously unknown to each other, communicate with each other wirelessly using short-range RF technology, said second communications device being at a certain moment of time in a first mode where the address of said second communications device is determinable by means of an inquiry wirelessly sent to it. In the method, the first communications device ( 10 ) sends ( 31 ) a first message in order to determine the address of said second communications device, said second communications device ( 20 ) receives ( 32 ) the first message, and said second communications device ( 20 ) generates and sends ( 33 ) to the first communications device a second message in response to the first message, the second message containing the address of said second communications device. In the method, a connection establishment process ( 35 - 38 ) is executed to establish a connection between the first communications device and said second communications device. During the connection establishment process, or in response to successful completion of the connection establishment process, at least one of said first and second communications devices ( 10, 20 ) switches ( 40 ) from said first mode into a second mode, in which second mode, the communications device that has switched into said second mode does not respond to messages arriving at it which have been sent to discover the address of the communications device that has switched into said second mode.

FIELD OF THE INVENTION

[0001] The present invention relates to the use of short-range RF (RadioFrequency) technology. Particularly, but not necessarily, the inventionrelates to preventing the discoverability of a wireless communicationsdevice employing Bluetooth technology.

BACKGROUND OF THE INVENTION

[0002] Bluetooth technology is a new technology for wirelesscommunications, enabling short-range wireless RF communications betweenmobile telephones, computers and PDA devices. Each Bluetooth device,i.e., any device supporting Bluetooth technology, will be equipped witha Bluetooth transceiver. This is a micro-chip, an integrated circuit,transmitting and receiving information such as voice or data wirelesslyon the 2.4 GHz frequency band. At present, the maximum range of aBluetooth connection using normal transmitter power is approximately 10meters.

[0003] Ericsson has introduced their Ericsson Bluetooth Headset HBH-10product. It is a headset comprising a microphone and speaker and usingBluetooth technology. The headset is intended to be used with a mobiletelephone equipped with Bluetooth features. After initiating a call fromthe mobile phone, the user can listen to the other party via the headsetspeaker and talk to the headset microphone. Between the mobile phone andthe headset, the call is transmitted over a Bluetooth connection.

[0004] Before using the headset for the first time, another device willbe assigned as the communications partner. From the point of view of themobile phone user, the headset HBH-10 and a Bluetooth-equipped mobilephone can be assigned as communications partners by the followingprocedure: First, the user selects the assignment function from theappropriate menu in the mobile phone. Then, the user enters theheadset's passkey into the mobile phone and presses the activation key.The mobile phone will start a search for Bluetooth devices within itsBluetooth operating range. The mobile phone will detect the headset, aswell as other devices that might be present within the Bluetoothoperating range, and their identifiers will be shown on the mobile phonedisplay. The user will select the identifier of the headset and pressthe activation key to assign the mobile phone and the headset as a pairof communications partners. The headset is now ready to be used with themobile phone.

[0005] In the Bluetooth specification, this procedure of assigning thecommunications partners is called the pairing procedure. The purpose ofthe pairing procedure is to establish a permanent trusted relationshipbetween two Bluetooth devices. This has the advantage, among others,that establishing a future connection between this pair of devices willbe simpler than establishing a connection between a pair of devicespreviously unknown to each other.

[0006] In the following, the pairing procedure and connectionestablishment in general will be examined in relation to the Bluetoothspecification in the case where the two devices are unknown to eachother. The Bluetooth devices will be designated the first Bluetoothdevice and the second Bluetooth device. The first Bluetooth device isthe one that initiates the pairing procedure. Before this, the firstBluetooth device must, however, determine the unique address (BluetoothDevice Address) of the second Bluetooth device.

[0007] To determine the address of the second Bluetooth device, thefirst Bluetooth device will send an inquiry message. The other Bluetoothdevice, as well as other Bluetooth devices that might be within theBluetooth operating range, will receive the inquiry message and generatean inquiry_res message in response; this message includes the address ofeach responding Bluetooth device. The Bluetooth devices will send theinquiry_res messages to the first Bluetooth device which will receivethem and thus get the addresses of the Bluetooth devices, including thatof the second Bluetooth device (from the inquiry_res message receivedfrom the second Bluetooth device). When the first Bluetooth device hasgotten the address of the second Bluetooth device, it can start thepairing procedure with the second Bluetooth device. First, the firstBluetooth device will generate a random number. It will send the randomnumber to the second Bluetooth device. The second Bluetooth device willreceive the random number and send an acknowledgement to the firstBluetooth device which will then receive the acknowledgement. Thepairing procedure will be continued as a multi-phased process designedto authenticate the first and the second Bluetooth device forestablishing a trusted relationship between the two devices. Duringdifferent phases of the pairing procedure, the random number mentionedabove, the secret key of the second Bluetooth device and the address ofthe second Bluetooth device, among other things, will be needed.Finally, the pairing procedure will generate a link key that will bestored in both devices. The link key will be linked with the addressesof the first and second Bluetooth devices. This can be done, forexample, by storing the link key adjacent to the second Bluetooth deviceaddress in the first Bluetooth device, and adjacent to the firstBluetooth device address in the second Bluetooth device. The link keycan later be used, among other purposes, for authentication and forgenerating an encryption key when establishing a Bluetooth connectionbetween the pair of devices. This is a typical mode of usage.

[0008] After generating the link key in the pairing procedure, aBluetooth connection will be established between the first Bluetoothdevice and the second Bluetooth device. Bluetooth connectionestablishment can be started with the link establishment procedure. Thelink establishment procedure is a multi-phase procedure designed toestablish a physical, Asynchronous Connection-Less (ACL) type linkbetween Bluetooth devices. The link establishment procedure is startedby sending a paging message from one Bluetooth device to the other.Typically, the first Bluetooth device initiates the establishment of theconnection and thus becomes the master in a master-slave arrangement;the second Bluetooth device becomes the slave.

[0009] After an ACL link has been established, a SCO (SynchronousConnection-Oriented) link can be established between the Bluetoothdevices using the SCO connection setup procedure.

[0010] The link establishment procedure is followed by the channelestablishment procedure, where a Bluetooth channel (logical connection)will be established between the Bluetooth devices. The channelestablishment procedure is followed by the connection establishmentprocedure, where the actual Bluetooth connection (application layerconnection) will finally be established between the Bluetooth devices.

[0011] After the Bluetooth connection has been established, informationsuch as voice or data can be transmitted over the Bluetooth connectionfrom one Bluetooth device to the other.

[0012] Each Bluetooth device can establish a pair with several otherBluetooth devices. In some cases, however, it might be desirable thatthe Bluetooth device forms a pair and establishes a connection with onlya few other Bluetooth devices or only a single device. The internationalpatent application PCT/FI01/00119 describes a Bluetooth smart cardreader which communicates information over a Bluetooth connectionbetween a smart card inserted in the reader and a mobile phone externalto the smart card reader. If said Bluetooth smart card reader is adevice intended for personal use, and it is desirable for securityreasons that the device only communicates with a single mobile phone,for example, it is unnecessary for such a Bluetooth smart card reader toannounce its address to other Bluetooth devices besides the mobilephone.

[0013] There may also be other situations where it is desirable forsecurity reasons that a personal Bluetooth device would not give itsaddress to unknown Bluetooth devices in order to prevent attempts ofunauthorized usage.

[0014] Also, if the user is listening to music using a Bluetoothheadset, that is a headset equipped with a Bluetooth transceiver, andthe music is transmitted, for example, from an MP3 player to the headsetover a Bluetooth connection, the Bluetooth headset may receive aninquiry message querying the addresses of the headset and otherBluetooth devices inside the Bluetooth operating range. When theBluetooth headset, which may have limited processing power, processesthe inquiry message, this may interfere with the music playback inprogress.

SUMMARY OF THE INVENTION

[0015] According to a first aspect of the invention there is provided amethod where a first communications device and a second communicationsdevice, previously unknown to each other, communicate with each otherwirelessly using short-range RF technology, the second communicationsdevice being, at a certain moment of time, in a first mode where theaddress of said second communications device is determinable by means ofan inquiry wirelessly sent to it, and in which method:

[0016] the first communications device sends a first message todetermine the address of the second communications device;

[0017] said second communications device receives the first message;

[0018] said second communications device generates and sends to thefirst communications device a second message in response to the firstmessage, said second message containing the address of said secondcommunications device;

[0019] a connection establishment process is carried out forestablishing a connection between the first communications device andsaid second communications device.

[0020] The method is characterised in that in the method:

[0021] during the connection establishment process, or in response tosuccessful completion of said connection establishment process, at leastone of said first and second communications devices switches from saidfirst mode into a second mode, in which second mode the communicationsdevice that has switched into said second mode does not respond tomessages arriving at it that have been sent in order to discover theaddress of the communications device that has switched into said secondmode.

[0022] In an embodiment of the invention, the first device and thesecond device are devices equipped with a Bluetooth transceiver.Preferably, said second mode into which at least one of said devicesswitches is a Bluetooth non-discoverable mode in which the device willnot respond to Bluetooth inquiry messages sent to query the address ofthe device. An advantage of the preferred embodiment is that afterentering non-discoverable mode, unknown parties cannot determine theaddress of the device if disclosure is not desirable, as the device willnot respond to inquiry messages. By entering non-discoverable mode, thedevice can also avoid unnecessary processing of inquiry messages andresponding to them, which saves processing resources in the device.

[0023] According to a second aspect of the invention there is provided afirst communications device comprising a transceiver for wirelesscommunication with a second communications device using short-range RFtechnology, the first communications device comprising two differentmodes, in the first mode of which the address of the firstcommunications device is determinable by means of a query wirelesslysent to it and in the second mode of which the address of the firstcommunications device is not determinable by means of a query wirelesslysent to it, the first communications device comprising:

[0024] said transceiver for receiving a first message sent by saidsecond communications device, said first message having been sent inorder to determine the address of said first communications device;

[0025] a processing unit and said transceiver for generating and sendinga second message to said second communications device in response to thefirst message, said second message containing the address of said firstcommunications device;

[0026] said processing unit and said transceiver for carrying out aconnection establishment process with said second communications deviceto establish a connection between said first communications device andsaid second communications device.

[0027] The first communications device is characterised in that thefirst communications device is configured:

[0028] to switch, during the connection establishment process or inresponse to successful completion of the connection establishmentprocess, from said first mode to a second mode in which second mode itdoes not respond to messages arriving at it which have been sent todiscover its address.

[0029] According to a third aspect of the invention there is provided afirst communications device comprising a transceiver for wirelesscommunication with a second communications device using short-range RFtechnology, the first communications device comprising two differentmodes, in the first mode of which the address of the firstcommunications device is determinable by means of a query wirelesslysent to it and in the second mode of which the address of the firstcommunications device is not determinable by means of a query wirelesslysent to it, the first communications device comprising:

[0030] said transceiver for sending a first message to said secondcommunications device in order to determine the address of said secondcommunications device;

[0031] said transceiver for receiving a second message sent by saidsecond communications device to said first communications device inresponse to the first message, said second message containing theaddress of said second communications device;

[0032] a processing unit and said transceiver for carrying out aconnection establishment process with said second communications deviceto establish a connection between said first communications device andsaid second communications device.

[0033] The first communications device is characterised in that thefirst communications device is configured:

[0034] to switch, during the connection establishment process or inresponse to successful completion of the connection establishmentprocess, from said first mode to a second mode in which second mode itdoes not respond to messages arriving at it which have been sent todiscover its address.

[0035] According to a fourth aspect of the invention there is provided acomputer program product executable in a first communications device andcomprising program code for:

[0036] causing the first communications device to communicate with asecond communications device using wireless short-range RF technology;

[0037] implementing a particular first mode of the first communicationsdevice in which first mode the address of the first communicationsdevice is determinable by means of a query wirelessly sent to it;

[0038] causing the first communications device to receive a firstmessage sent by said second communications device, said first messagehaving been sent in order to determine the address of said firstcommunications device;

[0039] causing the first communications device to generate and send tosaid second communications device a second message in response to thefirst message, said second message containing the address of said firstcommunications device; and causing said first communications device tocarry out a connection establishment process with said secondcommunications device to establish a connection between said firstcommunications device and said second communications device.

[0040] It is characteristic of the computer program product that thecomputer program product comprises program code for:

[0041] causing the first communications device to switch, during theconnection establishment process or in response to successful completionof the connection establishment process, from said first mode to asecond mode in which second mode it does not respond to messagesarriving at it which have been sent to discover its address.

[0042] According to a fifth aspect of the invention there is provided acomputer program product executable in a first communications device andcomprising program code for:

[0043] causing the first communications device to communicate with asecond communications device using wireless short-range RF technology;

[0044] implementing a particular first mode of the first communicationsdevice in which first mode the address of the first communicationsdevice is determinable by means of a query wirelessly sent to it;

[0045] causing the first communications device to send a first messageto said second communications device in order to determine the addressof said second communications device;

[0046] causing the first communications device to receive a secondmessage sent by said second communications device to said firstcommunications device in response to the first message, said secondmessage containing the address of said second communications device; and

[0047] causing said first communications device to carry out aconnection establishment process with said second communications deviceto establish a connection between said first communications device andsaid second communications device.

[0048] It is characteristic of the computer program product that thecomputer program product comprises program code for:

[0049] causing the first communications device to switch, during theconnection establishment process or in response to successful completionof the connection establishment process, from said first mode to asecond mode in which second mode it does not respond to messagesarriving at it which have been sent to discover its address.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In the following, the invention will be discussed in more detailby referring to the enclosed drawings, in which

[0051]FIG. 1 illustrates devices used in an embodiment of the invention,

[0052]FIG. 2 is a block diagram of a Bluetooth transceiver, and

[0053]FIG. 3 is a flow chart illustrating the various alternativeembodiments of a system according to the invention.

DETAILED DESCRIPTION

[0054]FIG. 1 illustrates devices used in a preferred embodiment of theinvention. These include a first wireless communications device 10 and asecond wireless communications device 20.

[0055] The first wireless communications device 10 comprises aprocessing unit μP10, a Bluetooth transceiver BT10 and a user interfaceUI10. The Bluetooth transceiver BT10 and the user interface UI10 areconnected to the processing unit μP10. The processing unit μP10comprises a microprocessor, microcontroller, digital signal processor orsimilar processing device, a memory MEM10 and software (one or moreapplications) SW10. The software SW10 is stored in the memory MEM10. Theuser interface UI10 provides the user with means for using the firstwireless communications device 10. The processing unit μP10 controls thefunctions of the first wireless communications device 10, such as theuse of the Bluetooth transceiver BT10, the presentation of informationin the user interface UI10 and the processing of information receivedfrom the user interface UI10, in accordance with software SW10. TheBluetooth transceiver BT10 comprises an antenna ANT10 through which theBluetooth transceiver BT10 is able to wirelessly transmit information tothe second wireless communications device 20 and receive informationfrom the second wireless communications device 20.

[0056] The second wireless communications device 20 comprises aprocessing unit μP20, a Bluetooth transceiver BT20 and a user interfaceUI20. The Bluetooth transceiver BT20 and the user interface UI20 areconnected to the processing unit μP20. The processing unit μP20comprises a microprocessor, microcontroller, digital signal processor orsimilar processing device, a memory MEM20 and software (one or moreapplications) SW20. The software SW20 is stored in the memory MEM20. Theuser interface UI20 provides the user with means for using the secondwireless communications device 20. The processing unit μP20 controls thefunctions of the second wireless communications device 20, such as theuse of the Bluetooth transceiver BT20, the presentation of informationin the user interface UI20 and the processing of information receivedfrom the user interface UI20, in accordance with software SW20. TheBluetooth transceiver BT20 comprises an antenna ANT20 through which theBluetooth transceiver BT20 is able to wirelessly transmit information tothe first wireless communications device 10 and receive information fromthe first wireless communications device 10.

[0057] The first and second wireless communications devices can be anykind of Bluetooth devices. For example, the first wireless communicationdevice 10 can be a cellular mobile telephone equipped with a Bluetoothtransceiver, and the second wireless communications device 20 can be aBluetooth smart card reader. If the first wireless communications device10 is a cellular mobile telephone, in addition to the blocks shown inFIG. 1, it comprises a RF section connected to the processing unit μP10for implementing the cellular network functions. Furthermore, the userinterface UI10 of the first wireless communications device 10 comprises,for example, a display, a keyboard, a microphone and a speaker. If thesecond wireless communications device 20 is a Bluetooth smart cardreader, in addition to the blocks shown in FIG. 1, it comprises a cardslot connected to the processing unit μP20 for receiving a smart cardinto the Bluetooth smart card reader.

[0058] Or, the first wireless communication device 10 can be a cellularmobile telephone equipped with a Bluetooth transceiver, and the secondwireless communications device 20 can be a Bluetooth headset. In thiscase, the user interface UI20 of the second wireless communicationsdevice (FIG. 1) comprises one or more speakers and possibly a microphoneconnected to the processing unit μP20.

[0059]FIG. 2 is a block diagram showing the blocks of the as such wellknown Bluetooth transceiver BT10. (The Bluetooth transceiver BT20 can beshown in the form of a similar block diagram.) The Bluetooth transceiverBT10 is implemented in a so-called Bluetooth module or Bluetooth chipwhich is a programmable integrated circuit unit comprising an RF-ASICcircuit (Radio Frequency Application Specific Integrated Circuit) and anantenna ANT10, a BB-ASIC circuit (BaseBand-Application SpecificIntegrated Circuit) and an electrically erasable FLASH memory.

[0060] The RF-ASIC is a radio frequency integrated circuit. It isconnected to the antenna ANT10. Using the antenna ANT10, the RF-ASICimplements a RF transceiver operating in the 2.4 GHz band.

[0061] The RF-ASIC and the FLASH memory are connected to the BB-ASIC.The BB-ASIC is a baseband integrated circuit that carries out theprocessing of baseband signals. The BB-ASIC implements a processing unitMCU that controls, with the aid of the FLASH memory, the overallfunctions of the Bluetooth transceiver BT10. The FLASH memory containsthe software for the Bluetooth transceiver, comprising the Bluetoothprotocols among other things. (Typically, the software comprises programcode written in an appropriate programming language.) The BB-ASIC isconnected to the processing unit μP10 via an appropriate bus (notshown), for example.

[0062] In a preferred embodiment of the invention, the pairing procedureis used to establish a trusted relationship between the first and secondwireless communications devices 10, 20 previously unknown to each other.After this, a Bluetooth connection will be established between thedevices for communicating information such as voice or data from onewireless communications device to another. The fact that the first andsecond wireless communications device are unknown to each other meansthat in the beginning, they have no knowledge of the other device'saddress.

[0063] In a preferred embodiment of the invention, of the wirelesscommunications devices 10, 20, the first wireless communications device(10) is the one taking the initiative. First, it must determine theunique address (Bluetooth Device Address) of the second wirelesscommunications device 20 to be able to start the pairing procedure withthe second wireless communications device 20. The processing unit MCU ofthe Bluetooth transceiver in the first wireless communications devicegenerates an inquiry message according to the Bluetooth protocol. Theprocessing unit transfers the inquiry message to the RF-ASIC of theBluetooth transceiver; after the necessary modulation operations, itwill transmit the inquiry message through its antenna ANT10. If it isdesirable that the inquiry message only reaches the second wirelesscommunications device 20 and no other devices, it can be arranged thatthere are no other devices but the second wireless communications device20 inside the Bluetooth range.

[0064] The Bluetooth transceiver BT20 in the second wirelesscommunications device receives the inquiry message through its antennaANT20; after the necessary demodulation operations, it will betransferred through the RF-ASIC to the processing unit MCU in theBB-ASIC. The processing unit generates an inquiry_res message inresponse to the inquiry message; the response contains the address ofthe second wireless communications device, specifically the BluetoothDevice Address of the Bluetooth transceiver BT20. The processing unitMCU transfers the inquiry_res message to the RF-ASIC of the Bluetoothtransceiver; after the necessary modulation operations, it will transmitthe inquiry_res message through its antenna ANT20 to the first wirelesscommunications device 10.

[0065] The Bluetooth transceiver BT10 in the first wirelesscommunications device receives the inquiry_res message through itsantenna ANT20; after the necessary demodulation operations, it will betransferred through the RF-ASIC to the processing unit MCU in theBB-ASIC, which will this way receive the address of the second wirelesscommunications device 20.

[0066] When the first wireless communications device 10 has gotten theaddress of the second wireless communications device 20, it can startthe pairing procedure with the second wireless communications device 20.In accordance with the master-slave principle, the first wirelesscommunications device 10 is the master in the pairing procedure (as itinitiates the procedure), and the second wireless communications device20 is the slave.

[0067] First, the processing unit MCU in the Bluetooth transceiver ofthe first wireless communications device 10 generates a random number.It transmits the random number to the second wireless communicationsdevice 20 through the Bluetooth transceiver BT10. The second wirelesscommunications device 20 will receive the random number through theBluetooth transceiver BT20 and send an acknowledgement to the firstwireless communications device which will then receive theacknowledgement. The pairing procedure will now continue as a multiphaseprocess, where the random number and the passkey of the second wirelesscommunications device 20 will be needed, among other data. The passkeyof the second wireless communications device can be queried from theuser, for example.

[0068] If the pairing procedure is successful, the first wirelesscommunications device 10 and the second wireless communications device20 will finally establish a link key that will be used as the foundationfor all securing actions (such as authentication and encryption keygeneration) for all upcoming Bluetooth connections established betweenthe first wireless communications device 10 and the second wirelesscommunications device 20.

[0069] The processing unit MCU in the Bluetooth transceiver BT10 of thefirst wireless communications device will store the link key in itsFLASH memory, and the processing unit MCU in the Bluetooth transceiverBT20 of the second wireless communications device will store the linkkey in its FLASH memory. The link key will be linked with the addressesof the first and second wireless communications devices. This can bedone, for example, by storing the link key adjacent to the address ofthe second wireless communications device 20 in the first wirelesscommunications device 10, and adjacent to the address of the firstwireless communications device 10 in the second wireless communicationsdevice 20. If the address of the second wireless communications device20 was not stored into the first wireless communications device 10before storing the link key, the address can be stored together with thelink key. Correspondingly, if the address of the first wirelesscommunications device 10 was not stored into the second wirelesscommunications device 20 before storing the link key, the address can bestored together with the link key. The second wireless communicationsdevice 20 gets the address of the first wireless communications device10 from the address field of the inquiry message, for example, or fromthe address field of any message sent by the first wirelesscommunications device 10 to the second wireless communications device 20during the pairing procedure.

[0070] The storing of link keys also means that the second wirelesscommunications device 20 will be marked as a trusted device in the firstwireless communications device 10, and the first wireless communicationsdevice 10 will be marked as a trusted device in the second wirelesscommunications device 20. This way, a trusted relationship has beenestablished between the first wireless communications device 10 and thesecond wireless communications device 20; the relationship is indicatedby storing connection information into both devices. In this context,connection information refers to the link key generated in the pairingprocedure and the addresses of the wireless communications devices 10,20. Because the connection information is stored in the pairingprocedure, establishing a future connection between this pair ofwireless communications devices will be simpler than establishing aconnection between a pair of devices previously unknown to each other.The pairing procedure will thus increase the user comfort of aBluetooth-equipped device. It must be noted, though, that a Bluetoothconnection between devices can also be established without the pairingprocedure.

[0071] In the following, the connection establishment process betweenthe first and second wireless communications devices will be describedin a case where the wireless communications devices 10, 20 have beenformed into a pair using the pairing procedure. After a successfulpairing procedure, the establishment of a Bluetooth connection betweenthe wireless communications devices 10, 20 can be started, for example,using the link establishment procedure. Because the Bluetooth connectionis established with a device marked as trusted in the pairing procedure,the Bluetooth connection to be established is usually called a trustedBluetooth connection. In a preferred embodiment of the invention, thefirst wireless communications device 10 initiates a connection with thelink establishment procedure by sending a paging message to the secondwireless communications device at the address of the second wirelesscommunications device 20; in accordance with the master-slave principle,the first device will become the master, and the second device willbecome the slave.

[0072] After an ACL link has been established using the linkestablishment procedure, a SCO (Synchronous Connection-Oriented) linkcan be established between the first and second wireless communicationsdevices 10, 20 by initiating the SCO connection setup procedure from thefirst wireless communications device 10.

[0073] When the link establishment procedure is completed, the firstwireless communications device 10 will start the channel establishmentprocedure, where a Bluetooth channel (logical connection) will beestablished between the wireless communications devices. After thechannel establishment procedure, the first wireless communicationsdevice 10 will initiate the connection establishment procedure, wherethe actual Bluetooth connection (application layer connection) willfinally be established between the first and second wirelesscommunications devices 10, 20.

[0074] After the Bluetooth connection has been established between thefirst and second wireless communications devices, information such asvoice or data can be transmitted over the Bluetooth connection from onewireless communications device to the other. This type of Bluetoothconnection, established between devices marked trusted by each other inthe pairing procedure, is called a trusted Bluetooth connection.

[0075] In a preferred embodiment of the invention, the second wirelesscommunications device 20 will, in response to the connectionestablishment process, enter a mode where it is hidden from otherBluetooth devices. Such a mode is defined in the Bluetooth specificationand called the non-discoverable mode. Here, “in response to theconnection establishment process” means that the second wirelesscommunications device 20 will enter non-discoverable mode at a suitablemoment during the connection establishment process or immediatelythereafter. In practice, such a suitable moment may be, for example,when the second wireless communications device 20 sends the firstwireless communications device a connect_est_acc message indicating tothe first wireless communications device 10 that the Bluetoothconnection has been established. Because the connect_est_acc messageends the connection establishment procedure, it can be stated that inthis case, the second wireless communications device 20 entersnon-discoverable mode in response to a successful connectionestablishment process.

[0076] While in non-discoverable mode, the Bluetooth device will notenter inquiry response mode. In other words, it will not respond toinquiry messages. After entering non-discoverable mode, unknown partieswill be unable to determine the address of the second wirelesscommunications device 20, because the second wireless communicationsdevice 20 will not respond to inquiry messages. The second wirelesscommunications device 20 can also avoid unnecessary processing ofinquiry messages and responding to them, which saves processingresources in the second wireless communications device 20. On the otherhand, as no response will be sent to the inquiry message, the firstwireless communications device 10 that sent the inquiry message will notget unnecessary address information from a wireless communicationsdevice 20 which it does not intend to communicate with. Security willalso be improved, as the address of the second wireless communicationsdevice 20 will not be available to all other Bluetooth devices sendinginquiry messages. Security will also be improved because as the secondwireless communications device 20 will not respond to inquiry messagesafter entering non-discoverable mode, it will not reveal its location tounknown Bluetooth devices sending inquiry messages nor to their users.

[0077] To establish a Bluetooth connection, only the address of theBluetooth device with which the connection is desired needs to be known.After the second wireless communications device 20 has enterednon-discoverable mode, a Bluetooth connection between a third Bluetoothdevice and the second wireless communications device 20 that is innon-discoverable mode can be established in a totally normal way if thethird Bluetooth device knows the address of the second wirelesscommunications device 20. To establish a Bluetooth connection, the thirdBluetooth device can, for example, initiate the link_establishmentprocedure by first sending the second wireless communications device 20a paging message. As the second wireless communications device 20 is innon-discoverable mode, though, it will not report its address toBluetooth devices that do not already know it. This way, unnecessaryconnection requests from unknown Bluetooth devices to the secondwireless communications device can be avoided.

[0078] As mentioned previously, a Bluetooth connection can also beestablished without the pairing procedure. (In this case, the Bluetoothconnection is not called a trusted Bluetooth connection, because theconnection is not established with a device marked as trusted.) In analternative embodiment of the invention, the first wirelesscommunications device 10, after getting the address of the secondwireless communications device 20 by means of the inquiry procedure,will start the connection establishment process without a pairingprocedure. Also in this case, the connection establishment processcomprises the link establishment, channel establishment and connectionestablishment procedures, and it is initiated with a paging message sentby the first wireless communications device 10 to the second wirelesscommunications device 20 at the address of the second wirelesscommunications device 20. Here, a link key will also be created for usewhen establishing the connection. However, this embodiment differs fromthe preferred embodiment where the connection between the wirelesscommunications devices was established through the pairing procedure inthat the link key will not be permanently stored into the wirelesscommunications devices 10, 20. That is, the same link key can not beused for new connections between the wireless communications devices 10and 20, but a new link key must be generated when establishing a newconnection. For example, if the first wireless communications device 10is a cellular mobile terminal and the second wireless communicationsdevice 20 is a beverage vending machine (Point-of-Sale terminal)equipped with a Bluetooth transceiver, enabling the wireless purchase ofbeverages using devices such as the first wireless communications devicethat can exist in millions, it would not always be reasonable to storeall the link keys into the limited memory of the vending machine. Inthis embodiment, the second wireless communications device 20 will enternon-discoverable mode in response to connection establishment, just asin the preferred embodiment of the invention. Nevertheless, if thevending machine is able to serve more than one wireless communicationsdevice at a time, it would not always be reasonable for the machine toenter non-discoverable mode in response to the first connectionestablishment. Alternatively, it will enter non-discoverable mode onlywhen its service capacity is full. This means that if the vendingmachine is able to serve, for example, eight Bluetooth devicessimultaneously, it would enter non-discoverable mode (typicallytemporarily rather than permanently) in response to the connectionestablishment process where the eighth simultaneous Bluetooth connectionis established. The device will enter non-discoverable modeautomatically (with no user intervention).

[0079] Correspondingly, if the second wireless communications device 20is a WLAN (Wireless Local Area Network) access point supporting, forexample, five simultaneous Bluetooth connection, it would enternon-discoverable mode in response to the connection establishmentprocess where the fifth simultaneous Bluetooth connection is establishedto the access point.

[0080] If the second wireless communications device 20 is a beveragevending machine or a WLAN access point, the term “wireless” refersprimarily to wireless communication of information.

[0081] The period that the wireless communications device 20 will stayin non-discoverable mode is dependent on the case. If the first wirelesscommunications device 10 is a cellular mobile terminal and the secondwireless communications device 20 is a personal device (such as apersonal Bluetooth smart card reader) intended to communicate with asingle user's mobile terminal only, it is appropriate for the wirelesscommunications device to permanently stay in non-discoverable mode. Inother words, it will not return to discovery mode without specialoperations. Such a special operation could be resetting the device,which would restore the second wireless communications device 20 to itsoriginal factory settings. Now, the second wireless communicationsdevice 20 will enter non-discoverable mode again in response to thefirst connection establishment process after reset.

[0082] In some cases, it may be appropriate that the second wirelesscommunications device 20 return from non-discoverable mode to discoverymode in response to a Bluetooth disconnection. In the beverage vendingmachine example above, the vending machine can return to discovery modewhen at least one Bluetooth connection through which beverages are beingpurchased is disconnected. In this case, the vending machine would thusreturn to discovery mode immediately after its service capacity has beenfreed by means of disconnecting a Bluetooth connection.

[0083] In an alternative embodiment of the invention, the secondwireless communications device will enter non-discoverable mode inresponse to the first connection establishment, but will always returnto discovery mode for a definite period (such as 30 seconds, 1 minute or2 minutes) in response to a certain operation that could be, forexample, the restarting of the second wireless communications device 20.After said definite period has elapsed, the second wirelesscommunications device 20 will automatically return to non-discoverablemode without user intervention. This embodiment is well suited for asituation where it is desirable that the second wireless communicationsdevice 20 stays in non-discoverable mode for almost all the time, butwhere there is a need to establish the second wireless communicationsdevice 20 as a pair with other Bluetooth devices besides the firstwireless communications device 10. If, for example, the second wirelesscommunications device 20 is a Bluetooth headset and the first wirelesscommunications device 10 is a cellular mobile telephone, the Bluetoothheadset will enter non-discoverable mode in response to the firstconnection establishment process initiated by the wirelesscommunications device 10. If the user desires to use the Bluetoothheadset to listen to a stereo radio equipped with a Bluetoothtransceiver, for example, the headset can be turned off and restarted.Now, the headset will be in discovery mode for a definite period duringwhich it is possible to carry out an inquiry procedure between thestereo radio and the headset, and possibly start the necessaryprocedures to form a pair and/or establish a Bluetooth connectionbetween the stereo radio and the Bluetooth headset.

[0084] In some cases, two Bluetooth devices can carry out a pairingprocedure a long time (such as several hours or days) beforeestablishing the first Bluetooth connection between the devices. Let usassume that a certain first Bluetooth device starts a pairing procedurewhere the other party is a certain second Bluetooth device. According toan embodiment of the invention, said second Bluetooth device will enternon-discoverable mode already in response to the pairing procedure andnot in response to the connection establishment process (as described inthe preferred embodiment of the invention). Especially if said secondBluetooth device (for example, a Bluetooth smart card reader) isspecifically intended to communicate with a single user's mobilecommunications terminal, in many cases it would not be appropriate thatthe other Bluetooth device would respond to inquiry messages betweencompleting the pairing procedure and initiating the connectionestablishment process.

[0085] If the second Bluetooth device enters non-discoverable mode inresponse to the pairing procedure, this means that it will enternon-discoverable mode at a suitable moment during the pairing procedureor immediately thereafter. In practice, such a suitable moment can befor example when the link key is stored in the Bluetooth device. Becausethe storage of the link key ends the successfully completed pairingprocedure, it can be stated that in this case, the second Bluetoothdevice enters non-discoverable mode in response to a successful pairingprocedure (or in response to the storage of the link key).

[0086]FIG. 3 is a flow chart that illustrates the functionalityaccording to the invention and its three alternatives. In block 31, thefirst wireless communications device 10 sends an inquiry message to getthe address of the second wireless communications device 20. In block32, the second wireless communications device 20 receives the inquirymessage. In block 33, the second wireless communications devicegenerates an inquiry_res message in response to the inquiry message,including the address of the second wireless communications device 20,and sends the inquiry_res message to the first wireless communicationsdevice 10. In block 34, the first wireless communications device 10receives the inquiry_res message and thus gets the address of the secondwireless communications device 20 for the pairing procedure and/or theconnection establishment process. In alternative 1, block 34 is followedby block 35 where the pairing procedure is carried out by initiative ofthe first wireless communications device 10. Block 35 is followed byblock 40 where the second wireless communications device 20 entersnon-discoverable mode in response to the pairing procedure. Inalternative 2, block 34 is followed by block 36 where, likewise, thepairing procedure is carried out by initiative of the first wirelesscommunications device 10. Block 36 is followed by block 37 where theconnection establishment process is carried out by initiative of thefirst wireless communications device 10. Block 37 is followed by block40 where the second wireless communications device 20 entersnon-discoverable mode in response to the connection establishmentprocess. In alternative 3, block 34 is followed by block 38 where theconnection establishment process without any pairing procedure iscarried out by initiative of the first wireless communications device10. Block 38 is followed by block 40 where the second wirelesscommunications device 20 enters non-discoverable mode in response to theconnection establishment process.

[0087] In this description, the pairing procedure and the connectionestablishment process have been treated as separate processes. However,it is also possible that the pairing procedure is rigidly connected withthe connection establishment process. This means that the pairingprocedure can be an inseparable part of the connection establishmentprocess. If this is the case, it can be stated that the Bluetooth devicereceiving the connection enters non-discovery mode in response to theconnection establishment process regardless of whether the Bluetoothdevice actually enters non-discovery mode in response to the pairingprocedure or at a later stage of the connection establishment process.

[0088] On the other hand, even if there was a break between the pairingprocedure and the connection establishment process, so that the pairingprocedure could not be considered an inseparable part of the connectionestablishment process, using a wide interpretation of the connectionestablishment process it could still be stated that the pairingprocedure is a part of the connection establishment process. Here, theconnection establishment process is defined as an entity that can coverboth the pairing procedure and the actual connection establishmentprocedures. The execution of actual connection establishment proceduresis also dependent on whether the pairing procedure has been executed ornot. So, even if the Bluetooth device would enter non-discoverable modein practice in response to the pairing procedure, it is correct to saythat it enters non-discoverable mode in response to the connectionestablishment process, because the pairing process can be consideredpart of the connection establishment process.

[0089] Even though it has been described here that only the wirelesscommunications device receiving the connection would enternon-discoverable mode, according to an alternative embodiment of theinvention it is possible that the wireless communications deviceinitiating the connection enters non-discoverable mode. In an embodimentof the invention, a certain first wireless communications device startsby querying the address of a certain second wireless communicationsdevice using an inquiry procedure. The first wireless communicationsdevice will now start a pairing procedure targeted at the secondwireless communications device. Nevertheless, the actual connectionestablishment procedures are started by said second wirelesscommunications device by sending a paging message to the first wirelesscommunications device (to the address of the first wirelesscommunications device). Said second wireless communications device willenter non-discoverable mode in response to the connection establishmentprocess, but the first wireless communications device will stay indiscovery mode. In this embodiment, the first wireless communicationsdevice can be, for example, a cellular mobile terminal, and the secondwireless communications device can be a Bluetooth smart card reader.After a successfully completed pairing procedure initiated by thecellular mobile terminal, the Bluetooth smart card reader can initiate aconnection to the mobile terminal automatically in response to smartcard insertion, for example, and then enter non-discoverable mode. (TheBluetooth smart card reader contains a sensor connected to theprocessing unit that will detect the insertion of a smart card into theBluetooth smart card reader.)

[0090] The invention can be implemented in software, in which case thenon-discoverable mode control software is a part of the Bluetoothtransceiver software stored in the FLASH memory (FIG. 2). The transitionto non-discoverable mode will be controlled by the processing unit MCUin the Bluetooth transceiver using the non-discoverable mode controlsoftware. This description presents the implementation and embodimentsof the present invention with the help of examples. It is obvious to aperson skilled in the art that the present invention is not restrictedto details of the embodiments presented above, and that the inventioncan also be implemented in another form without deviating from thecharacteristics of the invention. The invention must not be limited tothe messages and procedures expressly named in the description, forexample. With the appropriate changes, the pairing procedure, forexample, can be replaced with the bonding procedure known in Bluetoothtechnology. The invention must not be limited to Bluetooth technology,either, because the invention can also be applied to other similarsystems where information is communicated over a short-range RFconnection. The invention must not be limited to the structure of thefirst and second wireless communications devices presented here asexamples. For example, a wireless communications device does notnecessarily contain another processing unit besides the one in theBluetooth transceiver, but even the processing unit of the wirelesscommunications device may be integrated into the processing unit of theBluetooth transceiver.

[0091] The embodiments presented should thus be considered illustrative,but not restricting. Thus, the possibilities of implementing and usingthe invention are only restricted by the enclosed claims. The variousoptions of implementing the invention as determined by the claims,including the equivalent implementations, also belong to the scope ofthe invention.

1. A method where a first communications device and a secondcommunications device, previously unknown to each other, communicatewith each other wirelessly using short-range RF (Radio Frequency)technology, the second communications device being, at a certain momentof time, in a first mode where the address of said second communicationsdevice is determinable by means of an inquiry wirelessly sent to it, andin which method: the first communications device sends a first messageto determine the address of the second communications device; saidsecond communications device receives the first message; said secondcommunications device generates and sends to the first communicationsdevice a second message in response to the first message, said secondmessage containing the address of said second communications device; aconnection establishment process is carried out for establishing aconnection between the first communications device and said secondcommunications device, and wherein: during the connection establishmentprocess, or in response to successful completion of said connectionestablishment process, at least one of said first and secondcommunications devices switches from said first mode into a second mode,in which second mode the communications device that has switched intosaid second mode does not respond to messages arriving at it that havebeen sent in order to discover the address of the communications devicethat has switched into said second mode.
 2. A method according to claim1, wherein the connection establishment process is initiated by saidfirst communications device based on the address of said secondcommunications device.
 3. A method according to claims 1 or 2, whereinsaid second communications device switches into said second mode.
 4. Amethod according to claim 1, wherein only one of said first and secondcommunications devices switches into said second mode.
 5. A methodaccording to claim 1, wherein at least one of said first and secondcommunications devices switches into said second mode in response to apairing that is part of the connection establishment process.
 6. Amethod according to claim 1, wherein at least one of said first andsecond communications devices automatically switches into said secondmode in response to that connection establishment process that causesthe device's service capacity to be filled up.
 7. A method according toclaim 1, wherein the communications device that has switched into saidsecond mode returns from said second mode to said first mode in responseto a particular action.
 8. A method according to claim 1, wherein thecommunications device that has switched into said second mode returnsfrom said second mode to said first mode in response to a reset of saidsecond communications device.
 9. A method according to claim 1, whereinthe communications device that has switched into said second modereturns to said first mode for a definite period and after said definiteperiod has expired said communications device returns to said secondmode.
 10. A method according to claim 9, wherein the communicationsdevice that has switched into said second mode returns to said firstmode for the definite period in response to a restart of saidcommunications device.
 11. A method according to claim 1, wherein ashort-range RF connection is established between said first and secondcommunications devices in response to the connection establishmentprocess and that the communications device that has switched into saidsecond mode returns from said second mode to said first mode in responseto a disconnection of said short-range RF connection.
 12. A methodaccording to claim 1, wherein said first communications device and saidsecond communications device communicate using Bluetooth technology andsaid first message is an inquiry message according to Bluetoothtechnology and said second message is an inquiry_res message, said firstmode is the discoverable mode according to Bluetooth technology and saidsecond mode is the non-discoverable mode.
 13. A method according toclaim 1, wherein said first communications device is a cellular mobileterminal and said second communications device is one of the following:Bluetooth smart card reader, Bluetooth headset, WLAN (Wireless LocalArea Network) access point, POS (Point of Sale) terminal.
 14. A firstcommunications device comprising a transceiver for wirelesscommunication with a second communications device using short-range RFtechnology, the first communications device comprising two differentmodes, in the first mode of which the address of the firstcommunications device is determinable by means of a query wirelesslysent to it and in the second mode of which the address of the firstcommunications device is not determinable by means of a query wirelesslysent to it, the first communications device comprising: said transceiverfor receiving a first message sent by said second communications device,said first message having been sent in order to determine the address ofthe first communications device; a processing unit and said transceiverfor generating and sending a second message to said secondcommunications device in response to the first message, said secondmessage containing the address of said first communications device; saidprocessing unit and said transceiver for carrying out a connectionestablishment process with said second communications device toestablish a connection between said first communications device and saidsecond communications device, wherein said first communications deviceis configured: to switch, during the connection establishment process orin response to successful completion of the connection establishmentprocess, from said first mode to a second mode in which second mode itdoes not respond to messages arriving at it which have been sent todiscover its address.
 15. A first communications device comprising atransceiver for wireless communication with a second communicationsdevice using short-range RF technology, the first communications devicecomprising two different modes, in the first mode of which the addressof the first communications device is determinable by means of a querywirelessly sent to it and in the second mode of which the address of thefirst communications device is not determinable by means of a querywirelessly sent to it, the first communications device comprising: saidtransceiver for sending a first message to said second communicationsdevice in order to determine the address of said second communicationsdevice; said transceiver for receiving a second message sent by saidsecond communications device to said first communications device inresponse to the first message, said second message containing theaddress of said second communications device; a processing unit and saidtransceiver for carrying out a connection establishment process withsaid second communications device to establish a connection between saidfirst communications device and said second communications device,wherein said first communications device is configured: to switch,during the connection establishment process or in response to successfulcompletion of the connection establishment process, from said first modeto a second mode in which second mode it does not respond to messagesarriving at it which have been sent to discover its address.
 16. Acomputer program product executable in a first communications device andcomprising program code for: causing the first communications device tocommunicate with a second communications device using wirelessshort-range RF technology; implementing a particular first mode of thefirst communications device in which first mode the address of the firstcommunications device is determinable by means of a query wirelesslysent to it; causing the first communications device to receive a firstmessage sent by said second communications device, said first messagehaving been sent in order to determine the address of said firstcommunications device; causing the first communications device togenerate and send to said second communications device a second messagein response to the first message, said second message containing theaddress of said first communications device; and causing said firstcommunications device to carry out a connection establishment processwith said second communications device to establish a connection betweensaid first communications device and said second communications device,wherein said computer program product comprises program code for:causing the first communications device to switch, during the connectionestablishment process or in response to successful completion of theconnection establishment process, from said first mode to a second modein which second mode it does not respond to messages arriving at itwhich have been sent to discover its address.
 17. A computer programproduct executable in a first communications device and comprisingprogram code for: causing the first communications device to communicatewith a second communications device using wireless short-range RFtechnology; implementing a particular first mode of the firstcommunications device in which first mode the address of the firstcommunications device is determinable by means of a query wirelesslysent to it; causing the first communications device to send a firstmessage to said second communications device in order to determine theaddress of said second communications device; causing the firstcommunications device to receive a second message sent by said secondcommunications device to said first communications device in response tothe first message, said second message containing the address of saidsecond communications device; and causing said first communicationsdevice to carry out a connection establishment process with said secondcommunications device to establish a connection between said firstcommunications device and said second communications device, whereinsaid computer program product comprises program code for: causing thefirst communications device to switch, during the connectionestablishment process or in response to successful completion of theconnection establishment process, from said first mode to a second modein which second mode it does not respond to messages arriving at itwhich have been sent to discover its address.